11-Cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2-b:2′,3′-e][1,4]diazepin-6-one of Formula I, which is generically known as Nevirapine, is a non-nucleoside reverse transcriptase inhibitor with activity against Human Immunodeficiency Virus Type 1 (HIV-1). Nevirapine is marketed as tablets under the brand name VIRAMUNE and Nevirapine hemihydrate as oral suspension.
Nevirapine was first disclosed in U.S. Pat. No. 5,366,972. U.S. Pat. No. 5,366,972 discloses a process to prepare nevirapine, which is as summarized below:

3-Amino-2-chloro-4-methylpyridine of Formula A is condensed with 2-chloronicotinoyl chloride of Formula B to give 2-chloro-N-(2-chloro-4-methyl-3-pyridinyl)-3-pyridine carboxamide of Formula II, which is then reacted with cyclopropylamine to give N-(2-chloro-4-methyl-3-pyridyl)-2 -cyclopropylamino) -3-pyridine carboxamide of Formula III. Then N-(2-chloro-4-methyl-3-pyridyl)-2-(cyclopropylamino)-3-pyridine carboxamide was cyclized in the presence of sodium hydride to give nevirapine of Formula I. The disadvantage of the above process is use of large excess of cyclopropylamine. Further, with the above process undesirable side products are obtained during the reaction, which makes the product impure.
U.S. Pat. No. 5,569,760 discloses a process for the preparation of nevirapine, which comprises, the reaction of 2-chloro-N-(2-chloro-4-methyl-3-pyridinyl)-3-pyridine carboxamide with cyclopropylamine is carried out in the presence of a neutralizing agent, which is an oxide or hydroxide of an element of the second main or second subgroup of the periodic table. Calcium oxide is used preferably.
Surprisingly, it has now been found that the large excess of the relatively expensive cyclopropylamine may be reduced if the reaction is carried out in the presence of a reagent such as potassium fluoride or trisodium phosphate dodecahydrate.